1

The Forgotten Sun

Leif SvalgaardStanford University

SHINE-2011, Snowmass, CO13 July 2011

leif@leif.org

2

Solar Activity 1835-2011

0

10

20

30

40

50

60

1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Monthly Average Ap Index

0

2

4

6

8

10

1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

B nT

Year

B (IDV)

B (obs)

Heliospheric Magnetic Field Strength B (at Earth) Inferred from IDV and Observed

13 23

Sunspot Number

Ap Geomagnetic Index (mainly solar wind speed)

Heliospheric Magnetic Field at Earth

3

Summary of How the Sun is Similar Now to a Century ago

• Sunspot Number at Minimum was as low• Minimum lasted as long• Solar Wind Speed was Similarly Small• Heliospheric Magnetic Field was as small• Mid-century Solar Activity was Similarly High• Ca II Network was Similar to Today’s• Cycle 24 is now Predicted to be Low [‘lowest in a

hundred years…]

4

Reminder of the Near Zero Skill in Predicting the Solar Cycle (24)

0

5

10

15

20

25

30

0 25 50 75 100 125 150 175 200 225

Distribution of Predicted Solar Cycle 24 Size

Climatological Mean

Rmax

We seem to be here now

5

We have been there before, 108 years ago, but have largely forgotten how it was

2007.0422007.1212007.2032007.2852007.37

2007.4522007.5372007.6222007.7042007.7892007.8712007.9562008.0412008.1232008.2052008.2872008.3722008.4542008.5392008.6242008.7062008.7912008.8732008.9582009.0422009.1212009.203

2010.6112010.6922010.7742010.8552010.9372011.0422011.1212011.2032011.2852011.3662011.4482011.5292011.611

050

100150200250300350400450500

1980 1985 1990 1995 2000 2005 2010 2015

232221

Active Region Count

24

020406080

100120140160180200

1983 1984 1985 1986 1987 1988 1989 1990

21

22

020406080

100120140160180200

1993 1994 1995 1996 1997 1998 1999 2000

22

23

020406080

100120140160180200

2005 2006 2007 2008 2009 2010 2011 2012

23 24

6

Total Solar Irradiance has only been measured since 1978 and must be

‘reconstructed’ for times before that. Such reconstructions have a curious history as the ‘background’ variation

on which the obvious solar cycle variation of only 0.1% seems to ride had become smaller and smaller.

Shapiro et al., 2011

Recently, this issue has become ‘hot’ again with an inferred very large ‘secular’ trend since 1900.

This in spite of the Sun being so similar back then to now. What have we forgotten?

7

How Much of Climate Variation is Due to Variation of Solar Activity?

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Global Temperature Anomaly Reconstructions

ºC LoehleMobergGISS

Average

30-yr Averages

TSI (Steinhilber et al., 2009)

dTemp/Temp = ¼ * dTSI/TSI, so dTSI/TSI = 0.5% means dTemp = 0.4º

8

Is it that recent TSI is perhaps significantly

smaller now? As claimed by Fröhlich [his PMOD composite] and that a ‘fourth’ [non-magnetic]

parameter is needed: “It could be due to a global temperature change of

Sun of 0.25K”1360.2

1360.4

1360.6

1360.8

1361.0

1361.2

1361.4

2004 2005 2006 2007 2008 2009 2010 2011 2012

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

PMOD - 4.51

SORCE/TIM

Difference

Degradation of PMOD

1360

1361

1362

1363

1364

1365

1366

1367

0 1 2 3 4 5 6 7 8

1.003050

1.003100

1.003150

1.003200

1.003250

1.003300

1.003350

1.003400

1.003450

1.003500

1.003550

2004.0

PMOD

SORCE

Ratio

Comparison PMOD and SORCE-TIM

2005.0 2006.0 2010.02009.02008.02007.0 2011.0

SOHO Keyholes

2012.0

Monthly values

Comparison with SORCE/TIM suggests that PMOD has uncompensated degradation, and that there is no evidence for TSI this minimum being lower than at previous minima

9

Recent TSI Reconstructions are partly

calibrated using the PMOD smaller values the past minimum (and they were likely not smaller)

and an assumed secular change in the (Group) Sunspot Number. And

herein lies another problem: do we know the

sunspot number well enough for this?

Steinhilber et al., 2009

10

HMF From Ice Core 10Be

Steinhilber

11

The Sunspot Number(s)• Wolf Number = kW (10*G + S)

• G = number of groups• S = number of spots

• Group Number = 12 kG G

Rudolf Wolf (1816-1893) Observed 1849-1893

Ken Schatten

The ’12’ is to make the mean for the past ~100 years the same as the mean Wolf Number

0

2

4

6

8

10

12

14

1845 1850 1855 1860 1865 1870 1875 1880 1885 1890

Different Observers Have Different Group Counts

12

And Now, The Problem: Discordant Sunspot Numbers

Hoyt & Schatten, GRL 21, 1994

13

Major Adjustments to Wolf Number

2x‘1857’ 1.23x‘1874’

Wolf published several versions of his series over time, but did not modify his own data

Wolfer 0.58x‘1874’

Wolf

14

Justification of the Adjustments rests on Wolf’s Discovery: rD = a + b RW

.

H

North X

D

Y = H sin(D)

dY = H cos(D) dD

For small D, dD and dH

rY

Morning

Evening

East Y

rD

A current system in the ionosphere [E-layer] is created and maintained by solar FUV radiation. Its magnetic effect is measured on the ground.

15

The Diurnal Variation of the Declination for Low, Medium, and High Solar Activity

910

-10

-8

-6

-4

-2

0

2

4

6

8Diurnal Variation of Declination at Praha

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

dD' 1840-1849rD

-10

-8

-6

-4

-2

0

2

4

6

8Diurnal Variation of Declination at Praha (Pruhonice)

dD' 1957-1959

1964-1965

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

16

Wolf got Declination Ranges for Milan from Schiaparelli and it became clear that the pre-1849 SSNs were too low

The ‘1874’ list included the 25% [Wolf said 1/4] increase of the pre-1849 SSN

0

20

40

60

80

100

120

140

160

4 5 6 7 8 9 10 11 12 13

rD' Milan

R Wolf

'1861 List' 1836-1848Schwabe

'1861 List' 1849-1860Wolf

'1874 List' 1836-1873

Wolf = 1.23 Schwabe

Justification for Adjustment to 1874 List

17

The Wholesale Update of SSNs before 1849 is Clearly Seen in the Distribution of Daily SSNs

11 * 5/4 = 14

The smallest non-zero SSN is 11, but there are no 11s before 1849

18

Wolf’s SSN was consistent with his many-station compilation of the diurnal variation of Declination 1781-1880

First cycle of Dalton Minimum

It is important to note that the relationship is linear for calculating averages

19

Wolf used 4’ Fraunhofer telescopes with aperture 80 mm [Magn. X64]

Still in use today [by T. Friedli] continuing the Swiss tradition [under the auspices of the Rudolf Wolf Gesellshaft]

This is the ‘Norm’ Telescope

20

Wolf occasionally [and eventually – from 1870s on - exclusively] used much smaller handheld, portable

telescopes [due to frequent travel], leaving the 80mm for his assistants or when he was home

These telescopes also still exist and are still in use today to safeguard the stability of the seriesWolf estimated that to scale the count using the small telescopes to the 80mm Standard telescope, the count should be multiplied by 1.5

21

At some point during the 1940s the Zürich observers began to weight sunspots in their count

Weights [from 1 to 5] were assigned according to the size of a spot. Here is an example where the three spots present were counted as 9, inflating the sunspot number by 18% [(3*10+9)/(3*10+3)=1.18]

The weighting scheme is not generally known. One of those things that we have all forgotten.

22

What Do the Observers at Locarno Say About the Weighting Scheme:

“For sure the main goal of the former directors of the observatory in Zurich was to maintain the coherence and stability of the Wolf number, and changes in the method were not done just as fun. I can figure out that they gave a lot of importance to verify their method of counting. Nevertheless the decision to maintain as “secret" the true way to count is for sure source of problems now!”

(email 6-22-2011 from Michele Bianda, IRSOL, Locarno)

Sergio Cortesi started in 1957, still at it, and in a sense is the real keeper of the SSN, as SIDC normalizes everybody’s count to match Sergio’s

23

Corroborating Indications of the ‘Waldmeier Discontinuity’ ~1946

• SSN for Given Sunspot Area increased 21%• SSN for Given Ca II K-line index up 19%• SSN for Given Diurnal Variation of Day-side

Geomagnetic Field increased by 20%• Ionospheric Critical Frequency foF2 depends

strongly on solar activity. The slope of the correlation changed 20% between sunspot cycle 17 and 18

24

Illustrating that Observed Rz after 1945 is Higher than Deduced from Sunspot Areas

25

Ca II K-line Data Scaled to Rz shows similar Jump in Rz Sunspot Number after 1945

From ~40,000 CaK spectroheliograms from the 60-foot tower at Mount Wilson between 1915 and 1985, a daily index of the fractional area of the visible solar disk occupied by plages and active network has been constructed [Bertello et al., 2008]. Monthly averages of this index is strongly correlated with the sunspot number SSN = 27235 CaK – 67.14 [before 1946].

Waldmeier’s Sunspot Number 19% higher than Brunner’s from Ca II K-line

26

The Amplitude of the Diurnal Variation, rY, [from many stations] shows the same Change in Rz ~1945

27

The Ratio Group/Zurich SSN has Two Significant Discontinuities

At ~1946 (After Max Waldmeier took over) and at ~1885

28

Removing the Recent one [+20%] by Multiplying Rz before 1946 by 1.20, Yields

Leaving one significant discrepancy ~1885

29

y = 1.1254x + 4.5545

R2 = 0.9669

30

35

40

45

50

55

60

65

70

25 30 35 40 45 50 55

Helsinki, Nurmijärvi

rY '9-station Chain'

1884-1908 1953-2008

Scaling to 9-station chain Helsinki-Nurmijärvi Diurnal Variation

Helsinki and its replacement station Numijärvi scales the same way towards our composite of nine long-running observatories and can therefore be used to check the calibration of

303540455055606570

1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Helsinki Nurmijärvi

9-station Chain

rY nT

Range of Diurnal Variation of East Component

the sunspot number (or more correctly to reconstruct the F10.7 radio flux – see next slide)

30

The HLS-NUR data show that the Group Sunspot Number before 1880 must be Increased by a factor 1.64±0.15 to match rY (F10.7)

This conclusion is independent of the calibration of the Zürich SSN, Rz

31

Removing the Early one by multiplying Rg by 1.47, Yields

There is still some ‘fine structure’, but only TWO adjustments remove most of the disagreement

32

The Sunspot Number Series• The Zürich Sunspot Number, Rz, and the

Group Sunspot Number, Rg, can be reconciled by making only TWO adjustments:

• The first adjustment [20%] is to Rz ~1945

• The second adjustment [~50%] is to Rg ~1885

• No justification for secular trend

Of note is that there is no Modern Grand Maximum

33

That was the Past. How about the Future?

From 2001 to 2011 Livingston and Penn have measured field strength and brightness at the darkest position in umbrae of 1843 spots using the Zeeman splitting of the Fe 1564.8 nm line. Most observations are made in the morning [7h MST] when seeing is best. Livingston measures the absolute [true?] field strength averaged over his [small: 2.5″x2.5″] spectrograph aperture, and not the Line-of-Sight [LOS] field.

34

In spite of large scatter the magnetic field has decreased 500 G since 2000

Livingston also measures the intensity of the umbra compared to the continuum and finds that [in the infrared] that for all spots he can see [i.e. intensity < 1] the field is greater than ~1450 G. Another 500 G to go...

Hence his statement that if [when?] the decline of the field continues, spots will effectively ‘disappear’ or at least be much less visible.

0.0

0.2

0.4

0.6

0.8

1.0

2000 2005 2010

Intensity

Year

Umbral Intensity

1000

1500

2000

2500

3000

3500

4000

2000 2005 2010

B Gauss

Year

Umbral Magnetic Field

0.4

0.6

0.8

1

1000 1500 2000 2500 3000 3500 4000

Intensity

B Gauss

cycle 24

cycle 23

35

The Distribution of Field Strengths has Shifted with Time

Is this just a sunspot cycle dependence?

1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750

2009-2011

2005-2008

2001-2004

Gauss

Distribution of Sunspot Magnetic Field Strengths

36

Other indications of fewer spots?

y = -1.4940E-11x6 + 1.6779E-08x5 - 7.4743E-06x4 + 1.7030E-03x3 - 2.1083E-01x2 + 1.4616E+01x - 4.1029E+02

R2 = 0.9759

0

50

100

150

200

250

0 50 100 150 200 250 300

F10.7 sfu

R

Sunspot Number vs. F10.7 Flux Monthly Averages

1951-1990

1996-2011

Since ~1996 there have been fewer visible sunspots for a given F10.7 flux

37

The Observed Sunspot Number vs. that Calculated from the ‘old’ Relationship is too low Recently

Since the Sunspot Number is dominated by the number of small spots, the loss of visibility of small spots might be a natural explanation.

Was the Maunder Minimum just an example of an extreme L&P effect?

Is this happening again?

38

Similar effect seen in SSN compared to sunspot areas

39

Livingston, Penn, and Svalgaard:

Extrapolating the behavior from the past 13 years into the next 13 years suggests the Sun may enter a new Grand Minimum.

If true, we shall learn a lot about ‘The Forgotten Sun’ that nobody alive today has ever seen, with obvious implications for the climate debate and environmental issues generally.

Are there other indications that this might happen?

40

Where is the Extended Cycle?

Measurements of the location of ‘peaks’ of Fe XIV coronal emission at 503 nm (the ‘Green Line Corona’) over 7 solar cycles. The plots show the probability of observing a ‘peak’ at a given latitude as a function of time.

Altrock, 2011

TO: Hill, 2011

CYCLE 20

CYCLE 18

CYCLE 19

CYCLE 24

41

Fold South unto North

Sunspot, NM

Arosa, Switzerland

The Extended Cycle [if any] is not very clear

42

Our ‘Understanding’ of the Extended Cycle

Robbrecht et al. ApJ, 2010: “We conclude that the so-called extended cycle in coronal emission is a manifestation not of early new-cycle activity, but of poleward concentration of old-cycle trailing-polarity flux by meridional flow”

The red contours computed from PFSS coronal field (MWO)

43

Waldmeier also Interpreted The Green Line Emission as Marking the Boundary of the Polar Cap, ‘Rushing to the Pole’ when the

New Cycle Started

44

The angle between B and Br seems to show an ‘extended cycle’

45

The average signed magnetic field shows a large-scale structure without any hint of extended cycles

Solving the Enigma of the ‘Extended Cycle’ is a worthy Goal of SC24 Research

46

The Polar Fields are as Mysterious as Ever, perhaps Reversing Early

47

The HCS is Approaching Typical Solar ‘Maximum’ Inclinations

Unexpected early for a small solar cycle

48

Scattered Light Decreases Measured Magnetic Fields

y = 0.5424x

R2 = 0.8942

y = 0.5409x - 8.7224

R2 = 0.8956

-2000

-1500

-1000

-500

0

500

1000

1500

-4000 -3000 -2000 -1000 0 1000 2000

SN 706 vs. 705

13% uT

y = 0.6107x - 1.088

R2 = 0.9519

y = 0.6102x

R2 = 0.9516

-600

-400

-200

0

200

400

600

-1000 -500 0 500 1000

SN 9641 vs. 9640

uT8.81%

y = -0.0239x + 0.8792

R2 = 0.744

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12 14 16

% Scattered Light

Magnetic field reduction factor

16 May 2009

16 Sept 1978

Compare magnetograms taken with clean and dirty coelostat mirror

49

What a Mess!

Our time series of solar activity indicators are inconsistent and poorly calibrated.

People pick the ones they like in support of their pet theories.

We cannot provide other disciplines with properly vetted solar data

What to do about this?

50

Sunspot Workshop in 2011

Ed Cliver (Co-Organizer), Leif Svalgaard (Co-organizer), Rainer Arlt, K.S. Balasubramaniam, Luca Bertello, Tom Bogdan or Doug Biesecker, Frederic Clette, Ingrid Cnossen, Thierry Dudok de Wit, Peter Foukal, Thomas Friedli, David Hathaway, Carl Henney, Phil Judge, Ali Kilcik, Laure Lefevre, Bill Livingston, Jeff Morrill, Kalevi Mursula, Alexei Pevtsov, Art Richmond, Aaron Ridley, Alexis Rouillard, Ken Schatten, Ken Tapping, Jose Vaquero, Stephen White

We view the September workshop as the first step in an effort to provide the solar community with a vetted long-term sunspot number and the tools to keep it on track.

51

An ISSI Workshop in 2012

The Team proposal that you have submitted in response to the 2011 Call was evaluated by the Science Committee and the ISSI Directorate and considered to be of high scientific value and relevance . The proposal is thus approved for implementation.

International Teams in Space Science Proposal 2011

Title: Long-term reconstruction of Solar and Solar Wind Parameters

Co-Organizers: Leif Svalgaard (USA), Mike Lockwood (UK), Jürg Beer (Switzerland)

Team members: Andre Balogh (UK), Paul Charbonneau (Canada), Ed Cliver (USA), Nancy Crooker (USA), Marc DeRosa (USA), Ken McCracken (Australia), Matt Owens (UK), Pete Riley (USA), George Siscoe (USA), Sami Solanki (Germany), Friedhelm Steinhilber (Switzerland), Ilya Usoskin (Finland), Yi-Ming Wang (USA)